1. Field of the Invention
The present invention relates to a process for producing the magnesium salt of olefin sulfonic acids, and more specifically, it relates to a process for producing the magnesium salt of olefin sulfonic acids which contain only a small amount of unreacted magnesium compounds and do not cause the generation of foreign odor and color change.
2. Description of the Prior Art
Olefin sulfonic acids have been heretofore used as a surface-active agent, generally in the form of the sodium salt. However, recently, the magnesium salts of olefin sulfonic acids have become of major interest as a surface-active agent due to the fact that they have an excellent frothing property.
In the production of the magnesium salts of olefin sulfonic acids, when magnesium hydroxide and/or magnesium oxide are employed as a neutralizing agent, there are disadvantages in that extremely long operations for the neutralization of a alkene sulfonic acids and for the hydrolysis of sultone contained in the neutralization products are required. This is because magnesium hydroxide and oxide are only slightly soluble in water. The above-mentioned neutralization reaction can be more or less accelerated by heating the reaction system or by vigorously agitating the reaction system. However, in order to accelerate the above-mentioned hydrolysis reaction, the heating or the vigorous agitation of the reaction system is not practically applicable, due to the fact that acidification of the reaction system occurs. That is to say, the hydrolysis of the sultone comprises the ring opening (or cleavage) reaction of the sultone ring, and the neutralization reaction of the hydroxyalkane sulfonic acids and alkene sulfonic acids which are formed by the cleavage reaction of the sultone ring. However, if the dissolving rate of the magnesium compound necessary for the neutralization reaction is slow, the reaction system necessarily becomes acidic since the cleavage reaction is faster than the neutralization reaction.
As is well-known, the hydrolysis of the sultone under an acidic condition causes the generation of foreign odor and color change in the reaction products. It has not been proposed heretofore that the hydrolysis of the sultone can be accelerated without causing the above-mentioned problems. In the case where the sultone is hydrolyzed in the presence of a large excess of the magnesium compound, the hydrolysis can be somewhat accelerated and the generation of foreign odor and color change can be more or less depressed. However, this method is still not preferable, because a large amount of the unreacted magnesium compound remains, as an insoluble material, in the reaction products.